1. Field of the Invention
This invention relates to a percussion tool utilized for hitting a nail into a wood or the like material, equipped with a nail guide loading a nail, for example used in construction sites, to be hit by a driver blade equipped in a front end of the percussion tool.
2. Prior Art
FIGS. 5 and 6 schematically show a conventional percussion tool disclosed in the United States patent application No. 08/191,920, or in the Taiwanese utility model application No. 83202193, assigned to the same applicant as this application. The Japanese Utility model No. 6-5092 discloses the similar structure. As shown in FIGS. 5 and 6, the percussion tool has a nail guide 10 equipped at the front end thereof. The nail guide 10, having a hollow cylindrical body guiding the shaft portion of a nail 12, is provided with. a permanent magnet 19 attached at the lower end thereof for magnetically attracting or holding the shaft portion of the nail 12 at a retaining region 15 in the nail guide 10. Thus, the user can easily handle the percussion tool by a single hand because the nail 12 is magnetically retained in the injection portion of the percussion tool body 1, thereby providing handiness in a hitting operation of the nail 12 onto a wood 13 or the like material.
In the inner cylindrical wall of the nail guide 10, there is provided a stepdown region 14. Providing such a stepdown region 14 makes it possible to support or align the nail 12 in parallel with its hitting direction (i.e. an axial direction of a driver blade 7), when the nail 12 is inserted in the nail guide 10, because a larger-diameter head of the nail 12 is positioned in the stepdown region 14 while a smaller-diameter shaft of the nail 12 is held at the retaining region 15, i.e. a non-stepdown region, by the magnetic force of the permanent magnet 19. Furthermore, there is provided a slant surface 16 between the stepdown region 14 and the retaining region 15 so as to smoothly connect the stepdown region 14 to the retaining region 15, thereby guiding the inserted nail 12 somewhat obliquely along the slant surface 18 when the nail head is hit by a hitting face 17 of the distal end of the driver blade 7. In the drawings, reference numeral 9 represents a push lever, reference numeral 11 represents a blade guide, and reference numeral 90 represents a nail sensing portion.
In the beginning of a hitting or hammering operation of the above-described percussion tool, the nail 12 is magnetically held in the nail guide 10 and is laterally offset from the center of the driver blade 7, as shown in FIG. 5. When the driver blade 7 hits or hammers the nail 12, a hammering resistance force F1 acts against the nail 12 so excessively that the nail head is deformed by the hitting face 17 of the driver blade 7 causing a recessed portion 18 thereon.
When the nail 12 is forcibly advanced downward against this hammering resistance force F1 under the condition that the driver blade 7 is engaged with or locked into the recessed portion 18 of the nail head, the driver blade 7 is subjected to a strong deflection at the distal end thereof because it is bent by a significant amount of bending force F2 which is caused by the oblique advancement of the nail 12 guided by the slant surface 16. Thus, the significant amount bending force F2 acts against the driver blade 7 in the direction normal to the nail hitting direction, i.e. the axial direction of the driver blade 7.